Model a transparent body
This method is working suprisingly well in EEVEE. It's fully real time (fast, very fast). In Cycles also. And it is very flexible.



Material setup

Basically it is mix between Emission and Emission Transparent shader.

I've used Normal input to drive Facing Blend value, this is for making "highlights". Color Ramp is for fine tuning intensity of those highlights. By rotating sphere inside Normal node you can achieve many interesting setups. The one from example is pointing downwards.



Fresnel is used to make a bit of an outline around object.



EEVEE

To make it work in EEVEE you need to change material Blend Mode to Alpha Blend and turn of (if you need it) Show Backface.



Cycles

For Backfacing in Cycles you can use this setup. It's not working as well as in EEVEE but it is still good.